An outbreak of strangles in young ponies

Area of Science:

• Veterinary Medicine
• Equine Infectious Diseases
• Bacteriology

Background:

• Strangles, a highly contagious equine respiratory disease, poses significant challenges in herd health management.
• Natural outbreaks provide critical insights into disease dynamics and causative agents in susceptible populations.

Purpose of the Study:

• To document the clinical and microbiological features of a natural strangles outbreak in experimental ponies.
• To identify the specific beta-hemolytic streptococci involved and assess their persistence.

Main Methods:

• Monitoring of 19 young ponies following arrival at a veterinary school for clinical signs of strangles.
• Nasopharyngeal swabbing for bacterial isolation and identification.
• Hematological and plasma biochemical analyses (neutrophilia, fibrinogen levels).

Main Results:

• An 84% morbidity rate was observed, with typical strangles clinical signs including lymphadenitis and nasal discharge.
• Beta-hemolytic streptococci were isolated from 18 of 19 ponies; Streptococcus equi was confirmed in only 3 early cases.
• Streptococcus zooepidemicus was the predominant species identified; bacterial shedding persisted for weeks post-recovery in some ponies.

Conclusions:

• The outbreak demonstrated high morbidity and characteristic clinical signs of strangles.
• Streptococcus zooepidemicus played a significant role, with prolonged shedding observed even in recovered animals and in in-contact, non-clinically affected ponies.